CN113078833A - Vienna rectifier midpoint potential oscillation control method, system and device - Google Patents
Vienna rectifier midpoint potential oscillation control method, system and device Download PDFInfo
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- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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Abstract
The invention provides a method and a system device for controlling midpoint potential oscillation of a Vienna rectifier, wherein the method comprises the following steps of: determining a basic space voltage vector according to the current flow direction in the Vienna rectifier; constructing an alpha beta coordinate system, and determining a sector of a basic space voltage vector in the alpha beta coordinate system; selecting a basic space voltage vector of a sector, and solving the action time of an effective basic vector according to the basic space voltage vector; adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time; the method has good real-time performance, is beneficial to engineering practicality, effectively improves the quality of electric energy, reduces the cost, improves the overall performance and reliability of the three-level Vienna rectifier, and can be widely applied to the technical field of high power factor and high power density power electronics.
Description
Technical Field
The invention relates to the technical field of power electronics with high power factor and high power density, in particular to a method, a system and a device for controlling midpoint potential oscillation of a Vienna rectifier.
Background
With the urgent need for high power quality and power density rectifiers, three-level VIENNA (VIENNA) rectifiers have become a research hotspot at home and abroad in recent years, can realize input unit power factor correction, have the advantages of small harmonic wave, low switching loss, small electromagnetic interference and the like, have simple circuit structure, small number of switches and have no bridge arm direct connection problem, but have the problem of unbalanced neutral point potential direct current and alternating current.
The prior art has the advantages that the midpoint balance control is focused on solving the problem of direct current imbalance between an upper capacitor and a lower capacitor, and mature and feasible control methods and measures are provided for the direct current imbalance problem of the three-level converter. The problem of ac imbalance is solved by midpoint potential oscillation suppression, and unfortunately, the prior art focuses on the three-level converter midpoint potential oscillation suppression method, and the prior art focuses on the following methods: the oscillation of the midpoint potential is inhibited by adding a time offset, but the implementation method is complex, so that the instantaneity is poor; the neutral point potential oscillation is inhibited by calculating a neutral point potential compensation coefficient and dynamically compensating an injected zero sequence component, so that the problems of complex coordinate transformation and calculation, poor real-time performance and the like exist; the SPWM method is adopted to inhibit the midpoint oscillation, but the SPWM method has the defects of high switching loss and large output harmonic wave, and is not beneficial to engineering practicality; the discontinuous modulation is adopted to inhibit the oscillation of the midpoint potential, but the harmonic wave at the alternating current side is increased, and the quality of electric energy is reduced. Since the oscillation of the ac imbalance of the midpoint potential causes the existence of low-frequency harmonics, which in turn affects the power quality, the performance index requirements of the three-level VIENNA rectifier are very strict, and therefore, it is particularly important to study the oscillation suppression of the midpoint potential.
Disclosure of Invention
In view of this, to at least partially solve one of the above technical problems, an embodiment of the present invention aims to provide a method for optimally controlling midpoint potential oscillation of a VIENNA rectifier based on small vector adjustable, and also provides a system and a device capable of correspondingly implementing the method or function.
In a first aspect, the present disclosure provides a method for controlling a midpoint potential oscillation of a vienna rectifier, applied to the vienna rectifier, where the vienna rectifier includes a power tube, and the method includes: determining a basic space voltage vector according to the current flow direction in the Vienna rectifier;
constructing an alpha beta coordinate system, and determining a sector of the basic space voltage vector in the alpha beta coordinate system;
selecting a basic space voltage vector of the sector, and solving the action time of an effective basic vector according to the basic space voltage vector;
and adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time.
In a possible embodiment of the solution of the present application, the step of determining the basic space voltage vector according to the current flow direction in the vienna rectifier comprises:
determining the current flowing direction of each phase of the Vienna rectifier, and determining the switch combination state of the power tube;
and determining the basic space voltage vector according to the switch combination state.
In a possible embodiment of the solution of the present application, the step of constructing an α β coordinate system and determining a sector of the basic space voltage vector in the α β coordinate system includes:
dividing an alpha and beta coordinate space to obtain a plurality of first sectors according to the included angle between the basic space voltage vector and an alpha axis, and dividing the first sectors to obtain a plurality of second sectors;
transforming the basic space voltage vector to obtain an alpha beta coordinate vector, and determining the first sector according to the alpha beta coordinate vector;
and determining a first variable according to the alpha and beta coordinate vector, and determining a second sector where the basic space voltage vector is located according to the coordinate position relation of the first variable in the first sector.
In a possible embodiment of the present disclosure, the step of selecting the basic space voltage vector of the sector and solving the action time of the effective basic vector according to the basic space voltage vector includes:
and acquiring three nearest basic space voltage vectors of the first sector, and solving the action time of the effective basic vector according to a volt-second balance principle.
In a possible embodiment of the present disclosure, the adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power transistor according to the optimized action time includes:
combining the basic space voltage vectors to obtain a vector pair;
and changing the action duration of the basic space voltage vector in the vector pair, and keeping the action duration of the vector pair unchanged.
In a possible embodiment of the present disclosure, the step of changing the action duration of the basic space voltage vector in the vector pair to keep the action duration of the vector pair unchanged includes:
determining a midpoint potential fluctuation in the second sector;
changing the action time of the switching sequence, keeping the action time of the vector pair unchanged, and eliminating the midpoint potential fluctuation;
and according to the changed action time of the switching sequence, the action duration of the basic space voltage vector in the first sector is obtained by recursion.
In a second aspect, the present invention also provides a system for a vienna rectifier, the vienna rectifier including a power tube, including:
the adjusting module is used for determining a basic space voltage vector according to the current flow direction in the Vienna rectifier; constructing an alpha beta coordinate system, and according to the sector of the basic space voltage vector in the alpha beta coordinate system; selecting a basic space voltage vector of the sector, and solving the action time of an effective basic vector according to the basic space voltage vector; adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time;
and the rectifying module is used for converting the alternating current into the direct current according to the adjusting instruction of the adjusting module.
In a third aspect, the present invention provides a device for controlling midpoint potential oscillation of a vienna rectifier, including:
at least one processor;
at least one memory for storing at least one program;
when the at least one program is executed by the at least one processor, the at least one processor executes the vienna rectifier midpoint potential oscillation control method of the first aspect.
Advantages and benefits of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention:
the technical scheme of the application aims at basic space voltage vectors of current flow directions in each sector in an alpha beta coordinate system, the action time of the basic space voltage vectors in the corresponding sector is adjusted, and the turn-on and turn-off sequence of the power tube is controlled according to the optimized action time; the suppression of the neutral point potential oscillation can be effectively realized, and the harmonic wave of the input current at the three-phase alternating current side is obviously reduced; the method is simple, complex coordinate transformation and calculation are not needed, the real-time performance is good, engineering practicality is facilitated, the electric energy quality is effectively improved, the capacitance capacity of the direct current side and the capacitance of the alternating current side filter are reduced, the cost is reduced, and the overall performance and the reliability of the three-level VIENNA rectifier are further improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
Fig. 1 is a topology diagram of a three-level vienna rectifier according to an embodiment of the present invention;
fig. 2 is a flowchart illustrating steps of a method for controlling a midpoint potential oscillation of a vienna rectifier according to an embodiment of the present invention;
fig. 3 is a space vector diagram of a three-level vienna rectifier according to an embodiment of the present invention;
FIG. 4(a) is a schematic diagram of a switching sequence before time variation according to an embodiment of the present invention;
fig. 4(b) is a schematic diagram after the switching sequence is operated for time variation according to the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention. The step numbers in the following embodiments are provided only for convenience of illustration, the order between the steps is not limited at all, and the execution order of each step in the embodiments can be adapted according to the understanding of those skilled in the art.
The following explanations will first be made for related terms in the schemes of the present application:
the VIENNA rectifier (VIENNA) is a pulse width modulation rectifier, can receive three-phase alternating current power supply, and is also a power factor correction circuit;
the α β coordinate system refers to a two-phase stationary coordinate system.
In a first aspect, the technical solution of the present application provides a system capable of implementing optimization control of midpoint potential oscillation in a VIENNA rectifier based on small vector adjustment, which mainly includes an adjustment module and a rectification module, wherein the adjustment module is mainly used for performing optimization control of emphasis potential oscillation, and determines a basic space voltage vector mainly according to a current flow direction in the VIENNA rectifier; constructing an alpha beta coordinate system, and according to the sector of the basic space voltage vector in the alpha beta coordinate system; selecting a basic space voltage vector of a sector, and solving the action time of an effective basic vector according to the basic space voltage vector; and adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time. The rectifying module is mainly used for converting alternating current into direct current according to the adjusting instruction of the adjusting module.
In the embodiment, the rectifying module is mainly a VIENNA rectifier, which is essentially energy transfer, current flows from an alternating current side to a direct current side, the fundamental unbalance of midpoint potential is caused by different charging and discharging time of current flowing through a midpoint to upper and lower capacitors, the upper and lower capacitance values of the direct current side are fixed, the midpoint potential balance is controlled only from the control of midpoint current, the capacitor is an energy storage element, the midpoint current inevitably causes the change of stored charge of the capacitor when flowing through the upper and lower capacitors, so that the midpoint potential is unbalanced, and if the charge accumulation of the current flowing through the midpoint is balanced with the charge of the original midpoint potential, the midpoint potential can reach balance. The topology of the three-level VIENNA rectifier in this embodiment is shown in FIG. 1, where in FIG. 1, ea、eb、ecFor three-phase voltage of the grid, La=b=cAll are boost inductors; c1=2All are direct current side capacitors. In the VIENNA rectifier, each switching tube is subjected to a maximum voltage of half the output bus voltage.
In a second aspect, as shown in fig. 2, based on the system embodiment provided in the first aspect, the technical solution of the present application provides an embodiment of a method for controlling midpoint potential oscillation in a vienna rectifier, where the method includes steps S100-S400:
s100, determining a basic space voltage vector according to the current flow direction in the Vienna rectifier;
the basic space voltage vector is a combination of a plurality of switch states obtained according to the state of each phase of the three-phase VIENNA rectifier, and the basic space voltage vector is correspondingly obtained and comprises a zero vector, a small vector, a medium vector and a large vector, wherein only the small vector has a redundant vector.
S200, constructing an alpha beta coordinate system, and determining a sector of a basic space voltage vector in the alpha beta coordinate system;
specifically, in the embodiment, a large interval is divided by adopting a regular triangle, a coordinate system is divided into a plurality of large sectors, a plurality of small sectors are divided into the large sectors, when the large sector where a basic space voltage vector is located is judged and referred, a three-phase static coordinate system, namely an abc coordinate system, is subjected to coordinate transformation, a reference synthetic vector is used as a vector under a two-phase static coordinate, the large sector where the basic space voltage vector is located is judged by referring to the relationship between the synthetic vectors, and after the large sector is determined, the small sector where the basic space voltage vector is located is further judged according to the size of a variable by defining a new variable.
S300, selecting a basic space voltage vector of a sector, and solving the action time of an effective basic vector according to the basic space voltage vector;
specifically, three basic vectors nearest to the sector are selected according to the small sector where the reference synthetic vector is located, and the action time of the effective basic vector is solved according to the volt-second balance principle.
S400, adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time;
specifically, in order to optimize the midpoint potential oscillation, the midpoint potential fluctuation caused by the current flowing in the midpoint potential in each switching sequence is 0, the total action time of the small vector pair is kept unchanged by changing the action time of each small vector pair in each switching sequence, and the action time of other vectors is also kept unchanged, so that the midpoint potential oscillation can be optimized by adjusting according to the principle. Firstly, calculating the change time of the basic space voltage vector in one small sector, analogizing to all small sectors in the large sector, determining the change time of all basic space voltage vectors in the large sector according to the change time of the basic space voltage vectors in all small sectors, and analogizing to all large sectors. And finally, controlling the turn-on and turn-off sequence of the power tube according to the adjusted and optimized action time.
In some possible embodiments, the step S100 of determining the basic space voltage vector according to the current flow direction in the vienna rectifier may be further refined as: determining the current flow direction of each phase of the Vienna rectifier and determining the switch combination state; and determining a basic space voltage vector according to the switch combination state.
Specifically, since each phase in a three-phase VIENNA rectifier has 3 states: [ N ]]、[O]、[P]Wherein [ P]The state being current passing from the phase through the capacitor C1Flows to the midpoint O, [ O ]]The state is that the current flows directly from the phase to the midpoint O, [ N ]]For the current passing from the midpoint O through the capacitor C2And flows to the phase, so that the three phases have 27 switch state combinations, corresponding to 27 basic space voltage vectors, including 3 zero vectors (actually equivalent to 1 zero vector), 12 small vectors, 6 medium vectors and 6 large vectors, wherein redundant vectors exist only in the small vectors.
In some possible embodiments, an α β coordinate system is constructed, which may be further refined to steps S210-S230, according to the step S200 of the sector of the basic space voltage vector in the α β coordinate system:
s210, dividing an alpha beta coordinate space to obtain a plurality of first sectors and dividing the alpha beta coordinate space in the first sectors to obtain a plurality of second sectors according to the included angle between a basic space voltage vector and an alpha axis in an alpha beta coordinate system;
s220, transforming the basic space voltage vector to obtain an alpha beta coordinate vector, and determining a first sector according to the alpha beta coordinate vector;
and S230, determining a first variable according to the alpha and beta coordinate vector, and determining a second sector where the basic space voltage vector is located according to the coordinate position relation of the first variable in the first sector.
In steps S210-S230, the first sector refers to a large sector obtained by dividing the α β coordinate system space, and the second sector refers to a small sector obtained by further dividing the large sector; on an alpha-beta coordinate system, according to the included angle between the basic space voltage vector and an alpha axis, the basic space voltage vector is divided into 6 large sectors, each large sector is divided into 4 cells which are named as 1, 2, 3 and 4 respectively, wherein 3 and 4 are divided into 3a, 3b, 4a and 4b respectively for the convenience of analysis, and the space vector state is shown in fig. 3. In the embodiment, the relationship between the switch states and the midpoint current is shown in table 1, and the large vector and the zero vector do not influence the midpoint potential and are not listed in table 1.
TABLE 1
In the process of judging the large sector where the basic space voltage vector is located, the abc coordinate system uses the reference synthetic vector as a v under a two-phase static coordinate through coordinate transformationα、vβRepresents the large sector in which the large sector is located through the relationship between them, as shown in table 2:
TABLE 2
The small sector where the basic space voltage vector is located is further judged, the first sector in fig. 3 is taken as an example for judgment, and other large sectors are judged by a similar method. First three new variables are defined:
then the judgment of the small sectors 1, 2, 3a, 3b, 4a, 4b is shown in table 3:
TABLE 3
In some possible embodiments, the basic space voltage vector of the sector is selected, and the step S300 of solving the action time of the effective basic vector according to the basic space voltage vector may further be specifically: and acquiring three nearest basic space voltage vectors of the first sector, and solving the action time of the effective basic vector according to the volt-second balance principle.
Specifically, three basic vectors closest to the sector are selected according to the small sector where the reference synthetic vector is located, the action time of the effective basic vector is solved according to the volt-second balance principle, the action time before the basic vector in each cell of the first large sector is optimized is shown in table 4, and the action time of the basic vector in each cell of other sectors is similar.
TABLE 4
In the action time of Table 4, M is the modulation ratio, TsIs the switching tube cycle.
In some possible embodiments, the step S400 of adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time may be further detailed as steps S410-S420:
s410, combining the basic space voltage vectors to obtain a vector pair;
s420, changing the action duration of the basic space voltage vector in the vector pair, and keeping the action duration of the vector pair unchanged;
specifically, in order to optimize the midpoint potential oscillation, the midpoint potential fluctuation caused by the current flowing in the midpoint potential in each switching sequence is 0, the total action time of the small vector pair is kept unchanged by changing the action time of each small vector pair in each switching sequence, and the action time of other vectors is also kept unchanged, so that the midpoint potential oscillation can be optimized by adjusting according to the principle. The analysis is performed as follows, taking large sector 1 as an example, and other sectors are similarly analyzed.
(1) Small area 1:
the local switch sequence is [ ONN ] - [ PNN ] - [ PON ] - [ POO ] - [ PON ] - [ PNN ] - [ ONN ], and in general, the action time of [ POO ] and [ ONN ] is equal, as shown in FIG. 4(a), in this case, the current flowing into the midpoint caused by the middle vector [ PON ] is not 0, so that the midpoint potential oscillation is caused, the rising or falling of the potential depends on the direction of the B-phase current, and in order to counteract the potential oscillation caused by the middle vector, the action time of [ POO ] and [ ONN ] can be changed respectively:
Tdwell[PON]=2(Tc-Tb) (1)
Tdwell[ONN]=2Ta (2)
Tdwell[POO]=2(Tsw/2-Tc)=2Ta (3)
the magnitude Δ V of the midpoint potential fluctuation caused by the middle vector [ PON ] is:
i in the formulae (1) to (4)nIs the current at the middle of the cycle, TdwellIs a vector action time, e.g. Tdwell[PoN]Is [ PON ]]The action time, assuming that the current does not change in magnitude during a cycle, can be derived as:
in order to eliminate the fluctuating voltage, the total acting time of the pair of sinking small vectors is not changed by changing the acting time of each of [ ONN ] and [ POO ], and then:
due to the symmetry:
|2Ta|=|Tsw-2Tc| (7)
in the formula (8), Ia、Ib、IcRespectively corresponding to three-phase currents a, b and c, ToffTo change the time size; as shown in FIG. 4(b), in order to keep the midpoint voltage at 0, the [ PON ] is in this region]The flow into the midpoint during action causes the midpoint potential to rise [ ONN ]]Prolonged action time Toff,[POO]Decrease in action time of ToffThe other switching period time remains unchanged. Therefore, after the adjustment of the on-time, the action time of each segment of the small region 1 is as follows:
in formulae (9) to (10), Ta、Tb、TcCorresponding to a, b and c three-phase operation starting time, T'dwellIs adjusted vector motion duration, T'dwell[ONN]To be adjusted [ ONN](comprising two stages [ ONN]Other time periods are similar) motion duration, T'dwell[POO]To adjust [ POO ]]Duration of action, Tdwell[PoN]To adjust the first two [ PON ]]The duration of the segment motion is kept constant before and after the adjustment.
(2) Small area 2:
the seven-segment switch sequence in the small area is [ OON ] - [ PON ] - [ PPN ] - [ PON ] - [ OON ], which can be analyzed according to the same principle as the above-mentioned:
(3) small region 3 a:
the seven-segment switch sequences [ ONN ] - [ OON ] - [ PON ] - [ POO ] - [ PON ] - [ OON ] - [ ONN ] in the small area can be derived from table 1 according to the same principle as the above, and the vectors influencing the midpoint potential are [ ONN ], [ OON ], [ POO ], [ PON ] respectively according to the same principle as the above:
therefore, there are:
the other switching periods remain unchanged.
(4) Region 3 b:
the seven-segment switching sequence in this region is [ OON ] - [ PON ] - [ POO ] - [ PPO ] - [ POO ] - [ PON ] - [ OON ] as derived from Table 1 following the same principles as described above:
thus, in this sequence of switching cycles:
the other switching periods remain unchanged.
(5)4a region:
the seven-segment switch sequence in this region is [ ONN ] - [ OON ] - [ OOO ] - [ POO ] - [ OOO ] - [ OON ] - [ ONN ] according to the same principle as described above:
therefore, the method comprises the following steps:
the other sections remain unchanged in action time.
(6)4b region:
the seven-segment switching sequences [ OON ] - [ OOO ] - [ POO ] - [ PPO ] - [ POO ] - [ OOO ] - [ OON ] in this region are derived from the same principles as described above and are derived from Table 1:
therefore, the method comprises the following steps:
the other sections remain unchanged in action time.
In some possible embodiments, the step of changing the action duration of the basic space voltage vector in the vector pair and keeping the action duration of the vector pair unchanged further includes the step S430: and according to the changed action time of the switching sequence, the action duration of the basic space voltage vector in the first sector is obtained by recursion.
Specifically, taking the large sector i as an example, the time for adjusting each basic space voltage vector is summarized as shown in table 5:
TABLE 5
The adjustment times of the small sectors corresponding to the other large sectors are analogized according to the table 5. And the action time after the basic space voltage vector optimization of each cell of the first sector is as follows:
in small sector 1, vector [ POO]Time of action ofVector [ ONN]Time of action ofVector [ PNN]Time of action of (T ═ T)s[2sin(π/3-θ)-1](ii) a Vector [ PON ]]Action time T2TsMsinθ。
In small sector 2, vector PPN]Time of action of (T ═ T)s(2sin θ -1); vector [ PPO]Time of action ofVector [ OON]Time of action of Vector [ PON ]]Action time T2TsMsin(π/3-θ)。
In small sector 3a, vector [ POO]Time of action of Vector [ ONN]Time of action of Vector [ OON]Time of action of (T ═ T)s[1-2Msin(π/3-θ)](ii) a Vector [ PON ]]Time of action of (T ═ T)s[2sin(π/3+θ)-1]。
In small sector 3b, vector [ POO]Time of action of (T ═ T)s(1-2Msin θ); vector [ OON]Time of action ofVector [ PPO]Time of action of Vector [ PON ]]Time of action of (T ═ T)s[2sin(π/3+θ)-1]。
In the small sector 4a, the vector POO]Time of action ofVector [ ONN]Time of action ofVector [ O ]ON]Action time T2TsMsin θ; vector [ OOO ]]Time of action of (T ═ T)s[1-2Msin(π/3+θ)]。
In the small sector 4b, the vector [ POO]Action time T2TsMsin (π/3- θ); vector [ PPO]Time of action ofVector [ OON]Time of action ofVector [ OOO ]]Time of action of (T ═ T)s[1-2Msin(π/3+)]。
The action time after the optimization of each basic space voltage vector in other large sectors is obtained by analogy. And finally, controlling the turn-on and turn-off sequence of the power tube according to the adjusted and optimized action time.
In a third aspect, the present disclosure further provides a device for controlling a midpoint potential oscillation of a vienna rectifier, including at least one processor; at least one memory for storing at least one program; when the at least one program is executed by the at least one processor, the at least one processor is caused to execute the vienna rectifier midpoint potential oscillation control method as in the first aspect.
An embodiment of the present invention further provides a storage medium storing a program, where the program is executed by a processor to implement the method in the first aspect.
From the above specific implementation process, it can be concluded that the technical solution provided by the present invention has the following advantages or advantages compared to the prior art:
the invention can effectively realize the inhibition of the neutral point potential oscillation, obviously reduce the harmonic wave of the input current at the three-phase alternating current side, has simple implementation method, good real-time performance, does not need complex coordinate transformation and calculation, is beneficial to engineering practicality, effectively improves the electric energy quality, reduces the capacitance capacity of the direct current side and the capacitance of the alternating current side filter, reduces the cost and further improves the overall performance and the reliability of the three-level VIENNA rectifier.
In alternative embodiments, the functions/acts noted in the block diagrams may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Furthermore, the embodiments presented and described in the flow charts of the present invention are provided by way of example in order to provide a more thorough understanding of the technology. The disclosed methods are not limited to the operations and logic flows presented herein. Alternative embodiments are contemplated in which the order of various operations is changed and in which sub-operations described as part of larger operations are performed independently.
Furthermore, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise stated to the contrary, one or more of the functions and/or features may be integrated in a single physical device and/or software module, or one or more of the functions and/or features may be implemented in a separate physical device or software module. It will also be appreciated that a detailed discussion of the actual implementation of each module is not necessary for an understanding of the present invention. Rather, the actual implementation of the various functional modules in the apparatus disclosed herein will be understood within the ordinary skill of an engineer, given the nature, function, and internal relationship of the modules. Accordingly, those skilled in the art can, using ordinary skill, practice the invention as set forth in the claims without undue experimentation. It is also to be understood that the specific concepts disclosed are merely illustrative of and not intended to limit the scope of the invention, which is defined by the appended claims and their full scope of equivalents.
The logic and/or steps represented in the flowcharts or otherwise described herein, e.g., an ordered listing of executable instructions that can be considered to implement logical functions, can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A Vienna rectifier midpoint potential oscillation control method is applied to a Vienna rectifier, the Vienna rectifier comprises a power tube, and the method is characterized by comprising the following steps:
determining a basic space voltage vector according to the current flow direction in the Vienna rectifier;
constructing an alpha beta coordinate system, and determining a sector of the basic space voltage vector in the alpha beta coordinate system;
selecting a basic space voltage vector of the sector, and solving the action time of an effective basic vector according to the basic space voltage vector;
and adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time.
2. The vienna rectifier midpoint potential oscillation control method of claim 1, wherein the step of determining the fundamental space voltage vector according to the current flow direction in the vienna rectifier comprises:
determining the current flowing direction of each phase of the Vienna rectifier, and determining the switch combination state of the power tube;
and determining the basic space voltage vector according to the switch combination state.
3. The vienna rectifier midpoint potential oscillation control method of claim 1, wherein the step of constructing an α β coordinate system, and determining the sector of the basic space voltage vector in the α β coordinate system, comprises:
dividing an alpha and beta coordinate space to obtain a plurality of first sectors according to the included angle between the basic space voltage vector and an alpha axis, and dividing the first sectors to obtain a plurality of second sectors;
transforming the basic space voltage vector to obtain an alpha beta coordinate vector, and determining the first sector according to the alpha beta coordinate vector; and determining a first variable according to the alpha and beta coordinate vector, and determining a second sector where the basic space voltage vector is located according to the coordinate position relation of the first variable in the first sector.
4. The vienna rectifier midpoint potential oscillation control method of claim 3, wherein the step of selecting the basic space voltage vector of the sector and solving the action time of the effective basic vector according to the basic space voltage vector comprises:
and acquiring three nearest basic space voltage vectors of the first sector, and solving the action time of the effective basic vector according to a volt-second balance principle.
5. The vienna rectifier midpoint potential oscillation control method of claim 3, wherein the steps of adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time comprise:
combining the basic space voltage vectors to obtain a vector pair;
and changing the action duration of the basic space voltage vector in the vector pair, and keeping the action duration of the vector pair unchanged.
6. The vienna rectifier midpoint potential oscillation control method of claim 5, wherein the step of changing the duration of action of the fundamental space voltage vector of the vector pair to keep the duration of action of the vector pair constant comprises:
determining a midpoint potential fluctuation in the second sector;
changing the action time of the switching sequence, keeping the action time of the vector pair unchanged, and eliminating the midpoint potential fluctuation;
and according to the changed action time of the switching sequence, the action duration of the basic space voltage vector in the first sector is obtained by recursion.
7. A Vienna rectifier midpoint potential oscillation control system is applied to a Vienna rectifier, the Vienna rectifier comprises a power tube, and the system is characterized by comprising:
the adjusting module is used for determining a basic space voltage vector according to the current flow direction in the Vienna rectifier; constructing an alpha beta coordinate system, and according to the sector of the basic space voltage vector in the alpha beta coordinate system; selecting a basic space voltage vector of the sector, and solving the action time of an effective basic vector according to the basic space voltage vector; adjusting the change time of the basic space voltage vector, optimizing the action time according to the change time, and controlling the turn-on and turn-off sequence of the power tube according to the optimized action time;
and the rectifying module is used for converting the alternating current into the direct current according to the adjusting instruction of the adjusting module.
8. A vienna rectifier midpoint potential oscillation control device, comprising:
at least one processor;
at least one memory for storing at least one program;
when executed by the at least one processor, cause the at least one processor to perform the vienna rectifier midpoint potential oscillation control method of any one of claims 1-6.
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